Close #48 Allow base64 strings with missing equal signs at the end

JustTags/Utils/InputParser.swift

@@ -15,7 +15,7 @@ struct InputParser {
     }
 
     static func parse(input: String) throws -> [BERTLV] {
-        var parsedData: Data? = nil
+        var parsedData: [UInt8]? = nil
 
         let hexStringBytes = input
             .replacingOccurrences(of: " ", with: "")
@@ -26,11 +26,10 @@ struct InputParser {
         let compactedHexStringBytes = hexStringBytes.compactMap { $0 }
 
         if hexStringBytes.count == compactedHexStringBytes.count {
-            parsedData = Data(compactedHexStringBytes)
-        } else if let base64Bytes = Data(
-            base64Encoded: input, options: .ignoreUnknownCharacters
-        ) {
-            parsedData = Data(base64Bytes)
+            // Attempt parsing a hex string
+            parsedData = compactedHexStringBytes
+        } else if let base64Bytes = parseBase64(input: input) {
+            parsedData = base64Bytes
         }
 
         guard let parsedData = parsedData else {
@@ -40,4 +39,34 @@ struct InputParser {
         return try BERTLV.parse(bytes: [UInt8](parsedData))
     }
 
+    static private func parseBase64(input: String) -> [UInt8]? {
+        // Attempt parsing a base64 string
+        if let base64Bytes = Data(
+            base64Encoded: input, options: .ignoreUnknownCharacters
+        ) {
+            return [UInt8](base64Bytes)
+        }
+
+        // Attempt parsing a base64 string with missing padding
+        // Base64 data is encoded with groups of 4 characters
+        let groupSize = 4
+
+        // Check if the last group might be missing padding
+        let lastGroupSize = input.count % groupSize
+
+        // Only 2 and 3 characters in the last group are allowed
+        guard lastGroupSize == 2 || lastGroupSize == 3 else { return nil }
+
+        let paddedInput = input.appending(String(repeating: "=", count: groupSize - lastGroupSize))
+
+        if let base64Bytes = Data(
+            base64Encoded: paddedInput, options: .ignoreUnknownCharacters
+        ) {
+            // Attempt parsing a base64 string
+            return [UInt8](base64Bytes)
+        }
+
+        return nil
+    }
+
 }